Machine for making airplane propellers and the like



y 8, 1946. D. B. SALSTROM 2,400,954

MACHINE FOR MAKING AIRPLANE PROPELLERS AND THE LIKE Filed Dec. '23, 1942 s Sheets-sheet 1 May 28, 1946. D. B. SALSQTROM MACHINE FOR MAKING AIRPLANE PROPELLERS AND THE LIKE Filed Dec. 23, 1942 s Sheets-Sheet 2 mm E fi n Inge/afar Daaz'dBfiaZsimm May 28, 1946. D. B. SALSTROM 2,400,954

MACHINE FOR MAKING AIRPLANE PROPELLERS AND THE. LIKE '3 Sheets-$heet 5 Filed Dec. 25,1942

Patented May 28, 1946 MACHINE FOR MAKING AIRPLANE PROPELLERS AND THE LIKE David B. Salstrom, Chicago, Ill., assignor to Salstrom Carving Machine Company, Chicago, Ill., a corporation of Illinois Application December 23, 1942, Serial No. 469,911

10 Claims.

The invention relates to a machine for producing articles such as airplane propellers. It is well known that relatively slight departures from a predetermined standard contour an airplane propeller may result in a substantial decrease in eficiency. With this in View, the primary object of my invention is to provide a machine for reproducing faithfully the exact shape of a propeller which has been found in practice to possess maximum efficiency.

Another object is to provide for the production of propellers of high quality at a low cost.

The objects of the invention thus generally stated, together with other and ancillary advantages, are obtained by the construction and arrangement shown by way of illustration in the accompanying drawings forming a part hereof, in which:

Figure l is a fragmentary front elevational View of a machine embodying my invention.

Fig. 2 is a fragmentary plan view showing one group of cutters. V

Fig. 3 is an enlarged sectional view of the follower support, taken approximately in the plane of line 3-3 of Fig. 1.

Fig. 4 is an enlarged fragmentary transverse sectional view taken approximately in the plane of line 4-4 of Fig. 1.

Fig. 5 is an end View somewhat schematic in character and illustrating the control mechanism.

Fig. 6 is a schematic View illustrating the relative positions of the cutters and pattern follower, the work and pattern being shown intransverse section approximately at the position of line 5-4 of Fig. 7.

Fig. 7 is a plan view showing one end portion of a workpiece.

Fig. 8 is a fragmentary detail view of a pawl and ratchet feed mechanism.

The improved machine is of the type in which one or more cutters are controlled in their posi-- tiens relative to the work in accordance with the contour of a pattern; and in carrying out my invention I provide for the simultaneous operation by the cutters on opposite faces of the propeller blade in a manner such as to balance the forces applied to the blade transversely thereof whereby to avoid any distortion of the blade and at the same time simplify the means by which the work is supported. Preferably also, I provide for operation simultaneously upon a plurality of workpieces under the control of a single pattern and tracer or follower.

Referring now to Figs. 1, 2 and 3 of the drawings, the machine comprises in general a work and pattern supporting structure and a tool and follower structure mounted for relative movement, In the present instance the work and pattern are supported by a carriage mounted for movement in a front to rear direction relative to a stationary frame in which a plurality of cutters and followers are supported for cooperation with the workpieces and pattern. i

The specific construction of the work and pattern supporting carriage may be of any suitable or preferred character. As herein shown, the carriage comprises an upper horizontally disposed rectangular frame consisting of front and rear members It and Il (Fig. 5) and end members 12, and a pair of lower or supporting rails l3 secured at opposite ends of the frame by corner brackets l4 (Figs. 1 and 4).

The main or stationary framework of the machine is constructed to receive and support the work and pattern carriage formovement in a front to rear direction. It comprises a pair of base frame members [5 at opposite ends of the machine suitably connected by rods I6. Rollers H at the forward and rear ends of each of the base members l5 movably support the carriage.

For this purpose, the rails 13 of the carriage are T-shaped in form (Fig. 1) but inverted, the rollers engaging with the bottom faces of the rails. To guide the carriage in its front to rear reciprocation, suitable guide brackets l8 are mounted upon the base members [5 and slidably engage T-fianges of the rails 13.

Referring now to Figs. 4 and 7, the work and pattern carriage has a fixture bar 29 mounted upon the front member ll) of the carria and carrying a plurality of pillow blocks 2|, one for a pattern P and one for each of a plurality of workpieces W. The pillow blocks have inclined top faces forming seats for the central or hub portions of the propellers, the seats being inclined so that the blades proper will be disposed substantially in horizontal planes. The hub portions of the pattern and workpieces are fastened to the pillow blocks by'bolts 22, with rocker plates 23 interposed between the pillow'bl'ocks and hub portions of the propellers. The rocker plates have rounded faces engaging with the upper faces of the pillow block so as to permit rocking adjustment on a transverse axis and thereby facilitate clamping of thework and of the pattern in proper positions without placing the work under tension or strain.

' To support the tip ends of the pattern and workpieces, the carriage is provided with a longitudinal rail 24 spaced rearwardly an appropriate distance from the fixture bar 20 and having fastening bolts 25 equipped with hemispherical clamping nuts 26 between which the tip ends the respective cutters of each pair'yieldably urged against the opposite faces of the blank, and the cutters of each set so connected with the follower corresponding to that set as to move in unison according to the movements of the follower as determined by the shape of the pattern.

The cutters are in the form of relatively thin toothed disks 21 and the followers are preferably plain disks 28 of a thickness and diameter substantially corresponding to the cutters. Both the cutters and followers are supported for movement toward and from opposite faces of the workpieces orpattern. Additionally, the two sets of cutters together with their respective pattern followers are mounted for transverse feeding movement so that in successive reciprocations of the carriage the followers and cutters will be presented to different portions of the pattern and work respectively.

The means for thus supporting the two sets of cutters and their respective followers comprises in the present instance a pair of vertically spaced rods 29 and 38 extending lengthwise of the machine and slidably mounted at their opposite ends in a pair of central vertical standards 3| mounted upon the respective base members and connected by vertically spaced tubular members 32. The standards are also held rigid by diagonal brace members 33. The rods 29 and 30 are connected at the right-hand end (as shown in Fig. l) by a cross bar 34 so as to form a unitary support for the cutters movable lengthwise relative to the machine. Said rods are rotatable relative to the cross bar 34 and thus constitute rockshafts upon which are mounted a plurality of spaced parallel arms 35 carrying the cutters 2'! and the pattern followers 28.

In the present instance, th machine is adapted to shape eight propellers simultaneously so that there are sixteen cutters, two for each workpiece, and two followers for cooperation with opposite sides of the pattern. The cutters are arranged in two sets, namely an upper set and a lower set, and each set consists of two groups disposed respectively on opposite sides of the centrally disposed pattern (Fig. 1), there being two upper groups adapted to operate upon the upper faces of, the workpieces, and two lower groups'similarly operative on the lower faces.

t will be understood that the opposed sets of cutters operate first upon one end or blade of each propeller, whereupon the propellers are turnedend-for-end and the opposite ends formed. Also, before being operated upon in this machine, the blanks forming the workpieces are shaped to conform roughly or generally to the shape of the propeller. Thusthey are preliminarily shaped to provide a relatively heavy central portion or hub and from this central portion the blank gradually decreases in thickness to the tip ends thereof.

In each of the four groups the cutters 2'! are free ends of arms 35 on the rockshafts 29 and 30.

To support the cutters, each pair of arms 35 carries a spindle 36 journaled in a bearing head 31 connecting the free ends of the arms. In the case of the upper set of cutters, the arms 35 extend forwardly and somewhat downwardly from the rockshaft 29, and in the case of the lower set, the arms extend forwardly and somewhat upwardly. Adjacent their rear ends the arms of each pair are connected by a tie rod 38.

An electric drive motor 39 is provided for each group of four cutters. These motors are mounted upon frames or brackets 10 extending rearwardly from the respective rockshafts 29 and 30 and made rigid therewith. The motor drive shafts are equipped at opposite ends with suitable pulleys M connected by belts 42 with similar pulleys on the cutter spindles. The motors are slidably mounted upon their brackets and are yieldably held rearwardly so as to maintain the belts 42 under tension. In the present instance, a contractile spring 33 is connected by a chain 44 passing over asheave 45 for connection t the motor by links 46. The opposite ends of each spring are adjustably connected by a chain 44 to a tie rod fil extending through all of the pattern and cutter supporting arms 35 of each set near the free ends thereof.

The two sets of cutters are preferably urged toward the work by the action of a contractile spring 48 (Fig. 4) connecting opposed arms 35. The weight of the parts is so distributed in the case of each set of cutters that the drive motors and associated .parts tend to offset or counterbalance the weight of the cutters, etc. To equalize the forces applied to opposite sides of the work and pattern, counterbalancing weights 48 are added to the two upper groups of cutters. These weights are disposed at the side of the rockshaft 29 opposite the cutters, and each is adadjustably mounted on anarm 49 rigid with one of the motor-supporting brackets 43.

The tie rod 41 extending lengthwise of the machine and through thearms 35 supporting each set of cutters and followers, compels the cutters of that set to move vertically in unison with its follower. Thus, as the follower for each set of cutters moves up and down according to the curvatures of the pattern, corresponding movements are imparted to the cutters of that set. To permit adjustment of the cutters and followers relative to each other, the spindle bearings 31 are mounted on the ends of the arm 35 by means of bolts .33 entering through slots 5% in securing flanges 50 rigid with the spindle bearings. Moreover, the freeends of the arms may be provided with adjustment screws 5| to facilitate adjustment of the spindle bearings relative to the arms.

In view of the opposed relation of the cutters, means is provided to insure that the cutters will be held out of contact with each other in the absence of any pattern between the opposed cutters. For this purpose the safety disks 23' are provided, these disks being respectively rigid with the follower disks 28. They are made of a diameter slightly larger than the follower disks and arranged'in opposed relation so as to engage with each other before any possible interengagement by the cutters.

To reciprocate the work and pattern carriage, any suitable or preferred means may be employed. As herein shown, an electric motor 52 is mounted centrally of the machine substantially midway between the base members I and drives, through a speed reducer 52, a sprocket 53 connected by a chain 56 with a sprocket 55 fast on a pinion shaft 56. The latter is provided at opposite ends thereof with pinions 51 meshing with racks 58 which are secured to the undersides of the carriage rails l3 near the rear ends thereof.

The motor 52 is reversible and may be controlled to drive the carriage in one direction or the other in any suitable or well known manner. As shown in Fig. 5, the carriage is provide'd'with reversing dogs 59 andtil for cooperation with a reversing switch 6i suitably connected with the motor. Limit switches er and 63 are also preferably provided at the rear and forward ends respectively of one of the base frame members l5 for cooperation with stops at on the carriage rails ES to open the motor circuit inthe event that the reversing mechanism should for any reason fail to operate.

The means for feeding the cutter and follower support lengthwise of the machine and transversely of the pattern and workpieces may also be of any suitable orprefer'red character. In the present embodiment, the cross bar 34 at the right end of the cutter support has rigid therewith a'nut 65 for cooperation with a feed screw 65, For each reciprocation of the carriage, a

rotative rnovement is imparted to the s'crewfSB by a pawl and ratchet drive including a ratchet wheel 6'! and a pawl 68. T e latter is mounted upon an arm 69 rotatable upon a shaft it (Fig. 8) which forms an extension of the screw 86 and has the ratchet Wheel fast thereon. Rigid with the arm 69 is a sprocket ll connected by a chain 2 to a sprocket 73 on an actuating shaft 74 disposed below and parallel to the screw 66. The shaft M is suspended by brackets 74* (Fig. i) from the tie rod 32 and has a pinion 75 fast thereon for coaction with a rack bar iii mounted for sliding movement by brackets l1 upon the right-hand base member I5 (Fig. 4).

The rack bar 76 is actuated by dogs FE and is secured to the right-hand carriage rail l3 (Fig. 5). The arrangement is such that at the end of each forward movement of the carriage the dog 18 strikes the rack bar T6 and through the shaft it, chain I2 and ratchet device 68, 6S, imparts a rotative movement to the screw whereby to shift the cutter support one step and thereby shift the positions of the followers and cutters transversely with respect to the pattern and workpieces. At the end of the return movement of the carriage the pawl 69 is moved through an idle stroke preparatory to the next feeding movement.

The pattern P is in the main shaped accord the follower from running "off the pattern. The

trailing edge of the completed blade is extremely thin, being at its thinnest point about one-eighth of an inch thick, and it has been found that if the follower roller is permitted to leave the patternat this edge the cutters tend to produce a enetration or gouging of the work. To overcome this objection, the pattern is formed with a fin P conforming inthickness to the thickness of the trailing edge of the blade and forming in effect a lateral extension thereof. Preferably also, the fin is extended beyond the tip end of the blade and merges into an end fin P As shown in Fig. '7, the outer edge of the'fin P is parallel to the longitudinal axis of the pattern and thus is of suific ient width to support the follower throughout the entire movement of the carriage. In Fig. 6 I have shown the pattern and workpieces in transverse section approximately at the point of line 6-6 of Fig. '7, the shaping of the workpieces having been substantially completed;

In order to provide sufficient material for a final hand finishing operation, the follower is adjusted relative to' the cutters so that the work in its final form is of a thickness somewhat greater than the pattern. In the present instance, the followers are of the same diameter as the cutters and are adjusted relative to their supporting arms to offset the followers a small fraction, as for example, one thirty-second of an inch in the direction of the face of the work as shown in Fig. 3. It will of course be understood that the final hand finishing operation also includes the removal of fins corresponding to the fins P and P of the pattern.

It will be seen that by the use of opposed cutters operating simultaneously upon. the opposite faces of the work, I obtain a three-fold advantage, via, great accuracy due to the balance of forces and consequent lack of distortion, economy of operation because of the saving of time and labor, and simplification in mounting of the workpieces, it being only necessary to support the ends of the blades. While thQ'iI'lVGl'ltiOIl is especially suited for use in making airplane propellers, it is obvious that in its broader aspects it is susceptible of use in making other articles particularly where flexibility and possible distortion are disturbing factors.

I claim as my invention:

1. A machine for producing airplane propellers and the like comprising, in combination, a stationary frame, a carriage mounted for reciprocation relative to said frame and having means supporting a pattern together with a plurality of work blanks arranged in spaced parallel relation and extending in the direction of movement of the carriage with said pattern disposed substantially centrally of the work blanks, a support mounted in said frame for feeding movement transversely of the direction of reciprocation of the carriage, said support including a cross member disposed above said carriage and a second cross member disposed below the carriage, an upper and a lower set of cutters mounted on the respective members of said support for movement therewith, there being a pair of cutters for each work blank respectively urged into engagement with the upper and lower faces of the blank, a pair of followers also mounted upon said support and respectively engaging the upper and lower faces of the pattern, each set of cutters being connected for movement in unison with its corresponding follower, means for reciprocating the carriage, and means for imparting transverse feeding movements to the support in timed relation to the reciprocation of the carriage.

2. A machine of the character described comprising, in combination, meansjsupporting apattern to be traced and a blankto be shaped, a

pair of opposed rotary tracers positioned to simultaneously engage the opposite faces of said pattern, safety disks rigid with the respective tracers and mounted in opposed relation, a pair of rotary cutters of substantially the same dimensions as said followers arranged to simultaneously engage the opposite faces of said blank for reproducing in the latter the contours of the pattern encountered by said rotary tracers, said safety disks having a diameter slightly larger than said followers so as to maintain said cutters out of engagement with each other when said rotary tracers are out of engagement with the pattern.

3. A machine of the character described comprising, in combination, means for supporting a propeller pattern and a propeller blank in spaced parallel relation, means for simultaneously tracing the opposite faces of said pattern, means for simultaneously cutting into the opposite faces of supporting arms mounted upon the respective shafts and adapted to support a pair of cutters for engagement with opposite sides of the work blank simultaneously with the cutters arranged in opposed relation, a second pair of arms also mounted on said two shafts and having followers respectively engaging with opposite faces of said pattern, the arms on each of saidshafts being rigidly connected for movement in unison, means for effecting relative reciprocation between said supports lengthwise of the blank and pattern, and

- means for imparting relative transverse feeding said blank reproductions of the contours engaged by said tracing means, means for effecting continuous longitudinal movement of said pattern and blank relative to said tracing means and cutting means respectively, and means for effecting intermittent transverse movement of said pattern and blank relative to said tracing means and cutting means respectively. 7

4. A machine of the character described including, in combination, a pair of opposed supports each having a rotary tracer and a rotary cutter in diametrically opposed relation to the tracer and cutter of the opposite support, means urging said supports in a direction to carry said tracers and cutters toward one another for simovements between the supports in timed relation to said reciprocation.

8. In a machine for producing airplane propellers and the like, the combination of a pair of spaced parallel members adapted to support a work blank at longitudinally spaced points, together with a pattern in parallel relation to the blank, a pair of relatively thin cutter disks mounted for movement toward and from opposite sides of said blank and respectively urged toward the blank with both cutters exerting substantially uniform pressure'upon the blank from opposite sides thereof, follower means cooperating with said pattern and operative to control the movements of said cutters toward and from said blank, said follower means comprising a pair of relatively thin disks and all of said disks being multaneously engaging the opposite faces of a pattern and a blank, respectively, and means carried by one of said supports engageable with means carried by the other of said supports to insure a peripherally spaced relationship between said cutters in the absence of a pattern between said tracers;

5. In combination with a machine of the character described including means for simultaneously tracing and cutting the opposite faces of a propeller blank and a propeller pattern, respectively, means for supporting the propeller blank so as to leave the opposite faces free for action by said cutting means including a plate mounted to rock transversely of the longitudinal axis of the blank and adapted for engagement with the hub portion of the blank, and centering means engaging the tip portion of the blank.

6, In combination with a machine of the character described for simultaneously reproducing predetermined propeller'contours upon the opposite faces of a propeller blank, means for supporting said blank in a manner to leave the opposite faces free for the reproducing action including a member engaging the hub portion of the blank and arranged to permit a slight longitudinal rocking of the blank while preventing lateral rocking movement, and means for engaging the tip portion of the blank includin a pair of opposed semi-spherical members for engaging said tip portion at limited opposed points.

7. A machine for producing airplane propellers and the like comprising, in combination, a support comprising spaced parallel members to which opposite end portions of a, work blank and pattern may b secured in spaced parallel relation,

another support comprising a pair of spaced parallel shafts disposed respectively on opposite sides of the work blank and pattern, a pair of cutter mounted on the axes extending transversely of the axes of said blank and said pattern and engageable with opposite faces thereof, means for effecting relative reciprocation between the cutters and followers on the one hand and said blank and said pattern on the other hand in a direction lengthwise of the pattern and blank, and means for effecting relative transverse feeding movements between said cutters together with their followers and said pattern and blank.

9. In a machine for producing airplane propellers and the like, means for supporting a work blank in a horizontal position, a pair of rockshafts disposed above and below said blank and extending transversely thereof, arms rigid with each of said rockshafts and supporting cutters for engagement with the top and bottom sides of the blank, a, supporting bracket rigid with each of said arms and extending in a direction opposite thereto, an electric motor mounted on each of said brackets and connected to the respective cutters, spring means acting on saidarms to force them into engagement with the work, and a weight on both of said arms for equalizing the pressure exerted by the cutters against the work.

10. In a machine of the character described, in combination, a pair of vertically spaced supports each having a tracer and a cutter arranged in opposed relation to the tracer and cutter of the other support, said supports being movable to carry the opposed tracers and cutters toward and from each other, a carriage having a generallyrectangular frame adapted to be reciprocated horizontally between said supports, means on said frame supporting the pattern and blank at points spaced apart longitudinally thereof, said frame being open to permit the opposed tracers and cutters to maintain engagement with the upper and lower faces of the pattern and the blank while the carriage is reciprocated, and means carried by one of said supports engageable with means carried by the other of said supports for holding said cutters out of contact with each other when said tracers run off of the pattern.

, DAVID B. SALSTROM. 

